ACTION OF SALTS. 121 



The most active element in the pile, is the growing 

 plant. It is an acknowledged fact, that chemical 

 action, if not the source is ever attended by electri- 

 cal effects. An acid, in contact with an alkali, or 

 metal, always produces chemical action ; but the sil- 

 icates of the soil, are already combinations of acid 

 and metals ; hence as such, they have no tendency 

 to act on each other. If there be added to these a 

 salt or an acid, chemical action, decomposition be- 

 gins. The electricity is, we may say, excited by 

 salts — they are in this sense, and in no other, excit- 

 ants or stimulants. The very first act of vegetation, 

 the germination of seeds, induces this electric action, 

 this decomposition of the elements of soil. Germi- 

 nation produces carbonic acid, by decomposing wa- 

 ter. This has been so abundantly proved, by late 

 experiments in France, that it appears to be a good 

 argument against the theory, that the only action of 

 humus is, its production of carbonic acid, to supply 

 the wants of the plant, before nature has clothed it 

 with those organs of aspiration, the leaves, by which 

 the carbonic acid is withdrawn from the air. It 

 seems hardly probable that nature should require the 

 presence of humus or geine, merely as a laboratory 

 of carbonic acid, to supply the wants of the young 

 plant. The very first act of life in a seed is to 

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